Basis of Presentation and Significant Accounting Policies - Schedule of Changes in DAC due to Adoption of ASU 2018-12 (Details) - USD ($) $ in Millions	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	$ 332.9		$ 330.6
Whole Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	21.6	$ 21.2	20.9	$ 19.1	$ 17.8
Term Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	31.4	30.7	30.0	27.5	25.6
Experience Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	5.7	5.8	5.8	6.0	6.2
Limited Pay Whole Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	7.0	6.8	6.7	5.6	4.4
Indexed Universal Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	16.1	15.7	15.4	13.7	12.9
Supplemental health
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	7.0	6.7	6.2	4.9	4.3
Total Annuities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs	$ 217.2	$ 219.7	221.1	$ 223.3	223.1
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			433.1
Previously Reported | Whole Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					17.8
Previously Reported | Term Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					25.6
Previously Reported | Experience Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					2.6
Previously Reported | Limited Pay Whole Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					4.4
Previously Reported | Indexed Universal Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					11.3
Previously Reported | Supplemental health
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					4.3
Previously Reported | Total Annuities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					137.7
Effect of the Adoption of ASU 2018-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			$ (102.5)
Effect of the Adoption of ASU 2018-12 | Whole Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					0.0
Effect of the Adoption of ASU 2018-12 | Term Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					0.0
Effect of the Adoption of ASU 2018-12 | Experience Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					3.6
Effect of the Adoption of ASU 2018-12 | Limited Pay Whole Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					0.0
Effect of the Adoption of ASU 2018-12 | Indexed Universal Life
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					1.6
Effect of the Adoption of ASU 2018-12 | Supplemental health
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					0.0
Effect of the Adoption of ASU 2018-12 | Total Annuities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs					$ 85.4